Papermaking felt

ABSTRACT

A papermaking felt has an essentially three-layer construction including a cushion of non-woven batting material interposed between a relatively fine woven finish fabric and a preferably coarser woven wear fabric, and these respective portions of the felt are anchored together by one or more needling operations. The finish fabric is fine enough weave to prevent undesirable marking of a sheet of paper, and the wear fabric is strong enough in construction to resist the abrasion and wear and open enough to permit water to pass freely through the felt. The intermediate batt is thick enough to resist compression occasioned by the high pressures of normal paper machine speeds and joins the finish and wear fabrics in unitary construction to prevent the fabrics from shifting relative to each other during operation.

United States Patent lvanowicz [151 3,657,068 [4 1 Apr. 18, 1972 [54] PAPERMAKING FELT [21] App1.No.: 1,241

Primary Examiner-Charles Sukalo Assistant Examiner-Harry B. Ramey Attorney-Marechal, Biebel, French & Bugg [5 7] ABSTRACT A papermaking felt has an essentially three-layer construction including a cushion of non-woven batting material interposed between a relatively fine woven finish fabric and a preferably coarser woven wear fabric, and these respective portions of the felt are anchored together by one or more needling operations. The finish fabric is fine enough weave to prevent undesirable marking of a sheet of paper, and the wear fabric is strong enough in construction to resist the abrasion and wear and open enough to permit water to pass freely through the felt. The intermediate batt is thick enough to resist compres- [56] References Cited sion occasioned by the high pressures of normal paper UNITED STATES PATENTS machine speeds and joins the finish and wear fabrics in unitary construction to prevent the fabrics from shlftmg relative to 1,722,764 7/1929 Rasch ..161/80 each other during operation. 2,959,509 11/1960 Marsha11..... 3,214,327 10/1965 Wicker et a1 ..34/95 X 5 Claims, 4 Drawing Figures I v i 1 'I i l-EM, ,gmm liftiiiiWWWifiii'iiiiiiliiiii li ii i i li wiiilfli iiiifiillfiliiiiili gt 36 iiiiiilllligili i llillllill/piiitiiiliiigigiilii ii ilillilgilp .2 28 titty/lll ullt yiil tie/i yin l iliiiii ilm iliiiiiiiii i PATENTEBAPR 18 1922 3,657, 068

FIG-4 PRESS SEC 7' /ON PRESSURE H mm INVENTOR MICHAEL IVANOWICZ A TTOR/VE Y8 PAPERMAKING FELT BACKGROUND OF THE INVENTION The present invention relates to needled papermaking felts. Such felts are commonly used for supporting and draining paper making material during the papermaking process.

In recent years the speeds of papermaking operations have increased to the point that greater roll pressures have been necessitated which cause an increase in the tendency of felts to mark the sheets of paper as they pass through the nip and to wear excessively as they pass over the machine rolls, suction boxes, and cleaning equipment. The problems presented resulting from the increased production requirements vary depending upon the conditions under which the paperrnaking operation takes place (temperature, humidity, etc), the number of abrasive surfaces over which the felt travels, the condition of the papermaking machinery and various other factors known to persons skilled in the felt making art.

The ideal papennaking felt should have at least the following properties. First, it should have a surface that is fine enough to produce a smooth finish and minimize marking of the sheet of paper being produced. Second, it should be open enough to allow water to drain through it without significant impedance. Third, it should be resilient enough to quickly recover from repeated high nip pressures over a long period of time. Fourth, it should be tough and strong enough to provide good stability, wear resistance and felt life.

Batt-on-base needled felts which consist of a batt or fleece of loosely associated non-woven fibers needled to a woven base fabric are well known to the art and possess several of the characteristics of the ideal felt such as a smooth surface, and openness. Because of their relatively high drainage characteristics these felts have been extensively used throughout the papermaking industry.

However, several problems have been encountered with the batt-on-base needled felts. One problem is that the abrasive action of the press rolls causes the batt surface which receives the paper to shed fibers after a relatively short period of use. Such fibers cause printing problems and mark the paper, resulting in an inferior finished product. Another problem has been that the nip pressures pack down the batt to the point that the fibers are so closely spaced that the felts drainage characteristics are severely impaired. When the felts bulk and cushion properties are substantially reduced, the paper web is marked more readily. It has also been found that with these felts some of the water remaining within the batt fibers after water is expelled from the paper at the nip tends to seep back into the paper by capillary action to rewet the paper. When the batt is packed down the tendency for rewetting to occur is increased.

Another problem is that it has proven difficult to produce a needled felt which will withstand the excessive abrasion and wear caused by the pull of the paperrnaking machines under high roll pressures and speeds. The base fabric in such felts have of necessity been of a relatively fine construction so that the individual fibers could be adequately anchored to prevent shedding as much as possible, but fine base fabrics have relatively low stability and resistance to wear and abrasion and consequently such felts are plagued by distortion and have shorter service lives than is desirable.

SUMMARY OF THE INVENTION The present invention is directed to an improved felt which has increased bulk and cushion properties and increased wear resistance. The invention substantially increases felt service life by reducing shedding and increasing strength to meet the increased production speeds and pressures now common in the industry. Generally, the felt has an essentially three-layer construction comprising an intermediate batt or fleece of nonwoven material which is sufficiently thick to provide increased bulk and resilency for offsetting the higher nip pressures and which is bounded on one side by a relatively fine fabric for providing finishing quality and on the other side by a preferably coarser fabric for providing stability and wear re sistance. The internal batt is anchored to these fabrics preferably by a needling process to form a strong integral felt.

In accordance with a preferred embodiment of the present invention, the fine fabric is of a S-hamess satin-weave construction to provide a smooth surface which is relatively free of knuckles and cross-over marks in order that a high degree of finish may be obtained for the paper sheet. The coarse fabric is preferably of a plain-weave construction to provide for ease of drainage, and preferably has a high-synthetic content for added strength and wear resistance.

The felt is preferably made in the following manner. The fine fabric is woven and fulled as desired. It is then installed on a needle loom and non-woven batting material, which may be all wool, or a blend of synthetic and wool, or all synthetic, is applied to the back side thereof. The batting is of sufficient weight to give good bulk and cushion properties. The batting is then intimately anchored to the fine fabric by one or more needling operations. Next, a coarser fabric is inserted on the needle loom above the needled batting material and this fabric is needled into and through both the intermediate batting and the fine fabric.

The resulting felt has a smooth finish surface which effectively contains strike-through and shedding of the intermediate cushion material. The construction of the wear fabric pennits any water passing through the finish fabric and the cushion to drain from the felt with a minimum of impedence, while the intermediate cushion material not only adds resilience but also prevents the fabrics from shifting relative to each other. The fine finish fabric cooperates with the coarse wear fabric to help prevent water in the batting after it has passed the nip from seeping back into the web.

DETAILED DESCRIPTION OF THE DRAWING FIG. 1 is a perspective and somewhat diagramatic view showing the needling of a batt or fleece of non-woven batting material into the back of a fine finishing fabric;

FIG. 2 is a further somewhat diagramatic view showing the needling of a coarse wear fabric into and through the batting cushion and the fine finishing fabric;

FIG. 3 is an enlarged somewhat diagramatic transverse section through the felt at the completion of needling and showing the felt in its upright web supporting position; and,

FIG. 4 is a diagram of a paper machine press section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a fine fabric 10 which preferably has been finished to size is shown diagramatically as being positioned on the horizontal surface of a needling machine. It preferably has a relatively fine S-harness satin-weave construction (FIG. 3), wherein the yarns are single in both the warp and filling directions, but may be of a construction corresponding to any of the felt classifications ranging from Pulp, Common Wet, Fine Wet, Superfine Wet, Extra Superfine Wet, Fine Press, Super Press, Plate Press, Super Plate Press, and Yankee Pic-up. The fabric 10 may therefore be varied in design, yarns, weave, weight and end and pick count, as desired. The finish fabric 10 may be fulled or non-fulled and may be woven endless, but in practice it is preferred that it be formed as one length to be eventually spliced together to form an endless felt.

As shown in FIG. 1, a batt or fleece of non-woven batting material 12 which has preferably been finished to size is applied to the back 14 of the finish fabric 10. The batt of fibers 12 is preferably comparatively thick and has a weight on the order of 1/2 ounce per square foot, but the amount and weight thereof may be varied to suit different operating conditions and purposes. This batt material 12 is preferably a relatively fine grade of wool but a substantial portion or all of it may consist of synthetic material for purposes of increased bonding strength.

In practice, the batting material 12 may be needled into the finishing fabric 10 by two passes under the needling head 16 at 9/l6ths inch penetration and 1/ 12th inch advancement per stroke. The barbs 17 of needling head 16 are preferably oriented in the filling direction and are purposely fixed at incremental displacements which will penetrate the filling yarns l8 and minimize penetration of the warp yarns 20 (FIG. 3) so that these latter yarns which carry the load will not be substantially weakened. This is shown in the drawing by the greater number of fibers penetrating the filling yarns 18 as opposed to those penetrating the warp yarns 20.

The needling process compacts the batting material 12 against the back 14 of the fabric 10 so that it is intimately interlocked therewith and fills into the spacings, for example at point 22 (FIG. 3), between the hills 24 and the valleys 26 formed by the warp and filling yarns. In such a needling operation comparatively few of the fleecy fibers pass through the fabric.

After the batting has been needled to the finish fabric a second preferably coarser fabric 28 (FIG. 2) which has preferably been finished to size is threaded around the needled batt 12 already on the loom. Fabric 28, like fabric 10, may have a construction corresponding to any of the felt classifications depending upon the operating conditions and purposes. It may be all wool, or all synthetic, or a blend of wool and synthetic yarns, but is preferably comprised substantially or totally of tough and strong, highly synthetic yarns in both the warp and filling directions and may have a plain weave construction. The plain weave and the low end and pick count of this type of material will facilitate subsequent splicing when the three needled components are joined to form an endless felt.

The needling head 16 is brought into position (FIG. 2) and the wear fabric 28 is needled into and through both the intermediate batting cushion 12 and the finish fabric 10. This may be accomplished, for example, by using a /8th inch penetration and a 27/64ths inch advancement per stroke. Initially, only one round of needling is necessary. As before, the barbs 17 of the needling head 16 are preferably controlled to contact the filling yarns 30 and to minimize penetration of the warp yarns 32, and the needling process forces the wear fabric 28 into the batting 12 so that the batting fibers fill into the spacings, for example spacing 34, between the hills 36 and valleys 38 formed by the warp and filling yarns.

The felt of the present invention may as well be needled together by needling the batt material to the base fabric and then needling the fine fabric to the batt and base fabric. However, the method described above is preferred because after the barbs have passed into or through the finish fabric and are retracted they will pull some batt fibers back into the finish fabric. This method leaves fewer batt fibers on the surface of the finish fabric and minimizes scarring or tearing of the finish fabric.

The fabrics and 28 are not intended to be limited only to woven fabrics, but also may be non-woven fabrics, such as those made with dissolvable filler yarns in accordance with US. Pat. Nos. 3,401,467 and 3,458,91 l, issued to the same assignee herein. Such fabrics would, however, require that the barbs be oriented to anchor batting material to the warp yarns, and therefore woven fabrics with filler yarns are preferred.

The open ends of the resulting felt are spliced together and the entire fabric needled again at, for example, 5/8ths inch penetration and 9/64ths inch advancement per stroke to provide a second needling operation for forming an endless felt with thickness-interlocked fibers. The filling of the batting material into the respective valleys of the differently sized fabrics lends resilience to the felt. When combined with the strong fabric-to-fabric bonds formed by the needling operations, this filling also helps to prevent the fabrics from shifting relative to each other under the influence of high roll pressures (FIG. 4). Any strike-through which occurs is easily singed off and vacuumed away to produce a felt having a smooth, hair-free surface on the finishing side thereof and a tough surface on the driving side thereof.

A felt made according to the present invention was subjected to tension tests from 2,000 pounds to 10,000 pounds pressure, at 1,000 pound intervals, and showed no evidence of fabric separation or distortion. All three components were unifomily linked together to form a tough and strong integral felt. Shedding of batting material was essentially eliminated by reason of the presence of the finish fabric and the added anchoring of the batting material to two fabrics instead of one.

The felt of the present invention preferably has a substantial increase in thickness from an average thickness of 02,142 inch for the conventional batt-on-base needled felts to 02,645 inch, or on the order of about 23 percent increase. The somewhat thicker intermediate batting material acts as an absorber. Thus, the felt springs back or recovers more readily from high nip pressures of the rolls of a press section as shown in FIG. 4, and this resiliency is retained for a longer period of time than is possible with conventional felts.

In the preferred embodiment of the present invention the felt is normally heavier and thicker than conventional batt-onbase felts so that it can withstand distortion and deformation at high pressures. It has increased strength in both the warp and filling directions, and the finishing fabric withstands abrasion substantially more effectively than a batting finishing surface. I-Iaving a fabric for the finish surface keeps the felt open and helps to withstand the tendency of the batting material to compress. The coarse wear fabric resists wear and abrasion more effectively than the relatively light weight base fabrics used on conventional felts. Also, the combined fine construction of the finish fabric and coarse construction of the wear fabric causes the water in the batting material to move away from the web and drain through the wear fabric.

Accordingly, the felt of the present invention maximizes each of the four characteristics an ideal felt should have: finish, bulk and cushion, drainage, and wear resistance. It should be appreciated that the details of the needling process may be varied to achieve felts of different qualitative properties, such as by changing penetration, type of batting, batt mass, type of needle, needle penetration, fabric advancement, etc. without deviating from the concept of the present invention. Further, by varying the type of weave (plain, broken twill, 4-, 5-, or 6-harness satin, etc), the warp and filling yarns (weight, size, twist and ply) and the pick count of the respective fabrics, and by varying the thickness and type of batting materials, the openness and permeability of the felt may be changed to suit different web classifications. The respective fabrics may also be made wholly of synthetic materials, or contain a substantial portion of synthetic materials, and may be chemically treated or left untreated when shipped, as desired.

While the products herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise products, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A papermaking felt for supporting and draining a moving web of paper passing through papennaking machinery, comprising a woven finish fabric having warp and filling yarns forming hills and valleys, a woven wear fabric having warp and filling yarns forming hills and valleys, and an intermediate cushion of non-woven batting fibers pressed into said hills and valleys between said finish and wear fabrics and having thickness oriented fibers joined predominantly to the filling yarns of each of said fabrics preventing said fabrics from shifting relative to each other when in use and providing sufiicient bulk for the felt to recover readily from repeated operational pressures exerted thereon.

2. The felt of claim 1 wherein said finish fabric is of a relatively fine construction and said wear fabric is of a relatively coarse construction so that water in the batting material tends to move away from the web and drain through the wear fabric.

3. In a papermaking machine having a water removing press section in which a felt supports a web or sheet of paper through the nip of the press rolls for the removal of moisture therefrom, an improved felt structure for supporting the paper through the press rolls comprising:

a woven top fabric defining a fine and essentially non-marking finishing surface on which the paper is supported,

a woven base fabric which is coarser than said top fabric 5 and having an outer running surface in contact with said press rolls and providing dimensional stability and wear qualities to the felt, and

an intermediate layer comprising a non-woven fibrous material joined to said top and base fabrics to form a uni- 1O tary felt, said intermediate layer having a sufficient thickness to provide a cushion for said top fabric to assist in preventing marking of the paper by said press rolls and 

1. A papermaking felt for supporting and draining a moving web of paper passing through papermaking machinery, comprising a woven finish fabric having warp and filling yarns forming hills and valleys, a woven wear fabric having warp and filling yarns forming hills and valleys, and an intermediate cushion of nonwoven batting fibers pressed into said hills and valleys between said finish and wear fabrics and having thickness oriented fibers joined predominantly to the filling yarns of each of said fabrics preventing said fabrics from shifting relative to each other when in use and providing sufficient bulk for the felt to recover readily from repeated operational pressures exerted thereon.
 2. The felt of claim 1 wherein said finish fabric is of a relatively fine construction and said wear fabric is of a relatively coarse construction so that water in the batting material tends to move away from the web and drain through the wear fabric.
 3. In a papermaking machine having a water removing press section in which a felt supports a web or sheet of paper through the nip of the press rolls for the removal of moisture therefrom, an improved felt structure for supporting the paper through the press rolls comprising: a woven top fabric defining a fine and essentially non-marking finishing surface on which the paper is supported, a woven base fabric which is coarser than said top fabric and having an outer running surface in contact with said press rolls and providing dimensional stability and wear qualities to the felt, and an intermediate layer comprising a non-woven fibrous material joined to said top and base fabrics to form a unitary felt, said intermediate layer having a sufficient thickness to provide a cushion for said top fabric to assist in preventing marking of the paper by said press rolls and providing resilience and good draining qualities to the felt.
 4. The improvement of claim 3 in which the base fabric is formed with a weave which has a lower pick count and is more open than said top fabric to assist in providing draining qualities to the felt.
 5. The improvement of claim 3 in which said intermediate layer comprises non-woven fibers in which a high proportion of such fibers are thickness oriented and are interlocked with said top and base fabrics to assist in providing said draining qualities from said top fabric to said base fabric. 